Various types of milling apparatuses are known in the prior art. However, what is needed is a hydraulic injection milling apparatus with classifying screen that includes a hydraulic fluid injected into an impactor during operation, wherein crushed material delivered to the impactor is reducible to specific-sized particles transmittable through an interchangeable classifying screen disposed underlying a delivery aperture in the impactor, said classifying screen including a plurality of fixed width, elongate apertures disposed in parallel upon a durable plate member, said crushed material thus reduced in the impactor and thence classified through the classifying screen as fluid-borne sediment, deliverable for sorting and recovery, whereby coarse grain material is excluded by the classifying screen and yield from the impactor is increased by the hydraulic fluid washing sediment therefrom.